When an arc welding machine is not operating as desired, feedback signals are generally obtained and superimposed on electrical operating values of the welding machine, i.e., specifically welding current and voltage or a mathematical combination of these two quantities. The feedback signals represent a measure of the deviation, which can be used for optimum control of the welding machine.
The feedback signals are obtained either through the course of the welding process itself or through accessories which influence the welding process, for example, deflecting the arc from its stationary position. These feedback signals are typically obtained as a modulation of otherwise stationary operating values of the welding machine.
However, all operating data of an arc welding machine, such as arc current, arc flow, arc length, brightness, and temperature of arc, etc., have an inherent noise factor. Additional interference comes from fluctuations in the supply voltage for the welding machine. These noise factors are produced through material transfer in the arc, irregularities in the weld joint, irregularities in wire feed and wire size, and other factors.
It is therefore an object of the present invention to obtain the feedback signals from the welding machine so as to eliminate noise and other influences originating at the fluctuating energy source. These include fluctuations in voltage and pulsation of electrical operating values as occurring in welding energy sources employing bridge rectifiers.